Russian president Vladimir Putin will reportedly offer to supply missile systems to Iran and build a second nuclear power reactor in the country, a move likely to gladden Tehran and trouble the United States.

Iran's new president Hassan Rowhani is set to meet Mr Putin on the sidelines of a summit of the Shanghai Cooperation Organisation held in Kyrgyzstan on Friday, in the newly elected centrist cleric's first meeting with a major world leader.

The Kommersant business daily reported on Wednesday that Mr Putin will offer to supply Iran with S-300 air defence missile systems as well as build a second reactor at the Bushehr nuclear plant.

The S-300 offer would be a particularly contentious development given it would essentially revive a contract for similar missile systems that Russia cancelled in 2010 after heavy Israeli and US pressure.

Mr Putin's spokesman Dmitry Peskov told Kommersant that Mr Putin and Mr Rowhani were expected to discuss "working together in the nuclear energy sphere" and "questions of military technical cooperation" at the summit.

Mr Putin's meeting with the leader of Moscow's long-standing regional ally comes shortly after he hosted Western powers for a G20 summit focused on Syria in Saint Petersburg this month.

In 2007, Russia signed a contract to deliver five of the advanced S-300 ground-to-air weapons systems - which can take out aircraft or guided missiles - to Iran at a cost of $859 million.

However, in 2010, then-president Dmitry Medvedev cancelled the contract after coming under strong US and Israeli pressure not to go ahead with the sale of the weapons system, drawing vehement protests from Tehran.

Russia to supply Iran if US strikes Syria

Russia could increase supplies of arms to Iran if the United States decides on military intervention in Syria, the head of the lower house's committee on international relations, Alexei Pushkov, told parliament on Wednesday.

"If the 'party of war' prevails in the United States... then I consider it absolutely justified to suggest considering more serious measures by Russia, including broadening of supplies of defensive weapons to Iran," Mr Pushkov was quoted as saying by Interfax.

Iran is Syrian president Bashar al-Assad's main regional ally and has warned Western powers against intervention in the conflict.

Moscow has cooperated with Iran on nuclear power generation despite international opposition to a program that Western powers and Israel believe is being used as a smokescreen for building a nuclear bomb.

Iran, however, insists that its nuclear ambitions are peaceful.

Russia had urged the West to soften sanctions against Iran after the June election of Mr Rowhani, a centrist cleric, expressing hopes for a major breakthrough in the nuclear standoff.

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